The present invention relates to a waste water treatment apparatus and a waste water treatment method. The present invention relates to a waste water treatment apparatus and a waste water treatment method, as an example, which meet the total volume of nitrogen in conformity to partial revisions to Water Pollution Control Law implemented as of April 2004, and the emission reduction of toxic substances in conformity to PRTR (Pollutant Release and Transfer Register) Law implemented as of April 2001 (aminoethanol is one of the first-class designated chemicals in PRTR Law). The present invention relates to a waste water treatment apparatus and a waste water treatment method, as another example, which can microbially treat waste water containing aminoethanol discharged mainly from semiconductor plants without any dilution, and therefore which are excellent in initial, running and maintaining costs.
Conventionally, it has been impossible in general to microbially treat waste water containing aminoethanol, for a specific example, waste water containing high concentration aminoethanol of about 3000 ppm because aminoethanol has high microbial toxicity.
Even in the case where the waste water containing aminoethanol has been microbially treated, the microbial treatment has generally been performed at such a low concentration of aminoethanol as several hundred ppm.
Accordingly, the waste water containing high concentration aminoethanol of 3000 ppm or more has been concentrated to about 1/10 quantitatively by using an evaporator as a physical method. Thereafter, the concentrated waste water has been disposed as industrial waste.
In the method where the waste water is concentrated by using the evaporator, the amount of industrial waste from a plant is increased since the concentrated waste water is discharged from the plant as industrial waste. Generally, industrial waste including the concentrated waste water is disposed by incineration. The incineration causes a problem of air pollution due to use of fuels such as heavy oils. Further, the treatment using the evaporator or the like consumes a large amount of energy and involves large plant equipment. Thus causes a problem of large initial costs, running costs and maintenance costs.
JP 3467671 discloses a biological treatment method as a prior art. This biological treatment method is a nitrification and denitrification method. In the nitrification and denitrification method, organic waste water in a raw water tank is fed to a denitrification tank and a nitrification tank in series by using liquid supply pumps. Also, the organic waste water is circulated between both the above-stated tanks so that ammonia nitrogen contained in the organic waste water is reduced to nitrogen gas by using biological nitrification and denitrification actions, and thereafter nitrogen gas is removed. Sludge and treated water are separated from each other by using a suction pump and a filtration membrane unit which is dipped in the waste water contained in the nitrification tank.
The feature of the nitrification and denitrification method is that part of organic waste water fed from the denitrification tank to the nitrification tank is ejected to the organic waste water in the denitrification tank, wherein a conduit pipe for supplying the waste water from the denitrification tank to the nitrification tank is diverged so as to open ends of a diverged branch pipe in the waste water of the denitrification tank.
JP 3095620 discloses another biological treatment method as another conventional art. The biological treatment method is a method performed by a biological nitrogen removing apparatus. The biological nitrogen removing apparatus has a denitrification tank for receiving inflow of raw water containing organic substances, a nitrification tank for receiving inflow of denitrification tank mixtures from the denitrification tank, a nitrified liquid circulation channel for circulating nitrified liquid of the nitrification tank to the denitrification tank, and a nitrification tank diffuser placed inside the nitrification tank.
More specifically, the biological nitrogen removing apparatus is provided with a denitrification-bacteria-immobilization-carrier-filled zone in the denitrification tank so as to catch and remove suspended solids in the raw water flowing into the denitrification tank. Also, a raw water introduction channel and a nitrified liquid circulation channel are linked to a lower position of the denitrification tank which position is located under the denitrification-bacteria-immobilization-carrier-filled zone. A sludge hopper section is provided on the bottom of the denitrification tank, so that suspended solids, which are caught and removed by the denitrification-bacteria-immobilization-carrier-filled zone, are accumulated in the sludge hopper section. Further, a hopper diffuser is provided in the sludge hopper section.
As stated above, conventionally, waste water containing such high concentration aminoethanol as around 3000 ppm has not been microbially treated because of high biological toxicity. Therefore, the waste water containing high concentration aminoethanol has been treated by using the above-mentioned concentration method.
In the concentration method, however, as stated above, there are the problems of heavy consumption in energy and increase in industrial waste of concentrated waste water.